The present invention relates to a device to assist in retrieving geotechnical and environmental soil samples, and in particular, to an adapter coupling for connecting a soil sampling barrel to a drill rod wherein the adapter coupling allows the sampling barrel to receive only downward motion of a vibrating drill rod.
Earth probing for environmental and geotechnical soil sampling has become increasingly necessary. Samples may be taken by drilling into the earth and taking samples at predetermined depths, or by driving samplers into the earth. Where possible, driving samplers directly is usually less expensive and more convenient than drilling. Often, a number of samplers must be driven at a site, and it is desirable that these samplers be installed as quickly as possible. Sonic drilling is a fast way of driving samplers, in which vibratory energy is applied to a drill rod at a resonate frequency which multiplies the force applied at the drilling spindle many times as it is transmitted to a bit within the ground and also tends to fluidize or break apart the surrounding particles in the earth. Since the frequency of the vibrations is normally 50–150 Hertz, which is in the sonic range, installation of samplers in the ground by applying vibratory energy is commonly referred to as “sonic drilling.” Sonic drilling permits installation of samplers at a very rapid rate. In addition to earth probing, sonic energy can be used to facilitate installation of other objects into the ground.
Samplers used to obtain geotechnical and environmental soil samplers typically use a split barrel design. A complete split barrel sampler assembly consists of a drive shoe for driving into the soil, a two-piece split barrel sampler, and an adapter coupling. The split barrel sampler is a tubular member, typically having a round cross-section, split lengthwise to facilitate removal of soil samples contained therein after it is driven in the earth. Typically both ends of the split barrel sampler are externally threaded, and the drive shoe contains a tapered tip on one end for effectively cutting through soil, and an internal thread on the opposite end for mating with the split barrel sampler.
Typically the split barrel is attached to a drill rod with an adapter coupling that has internal threads on one end for mating with the drill rod and internal threads on the opposite end for mating with the split barrel.
If the sampler is vibrated into the ground, as occurs with sonic drilling, the up and down motion may cause the sample to be disturbed. Since it is important for accurate samples to be taken, this disturbance can make the soil sample suspect. In addition, the up and down vibrator motion of a sonic drill generates a tremendous amount of friction and associated heat between the barrel sampler and the ground that may affect the integrity of the sample.
Therefore, it is an object of the invention to provide a soil sampling system that minimizes the amount of disturbance of soil samples taken with the vibratory drill. It is another object of the invention to provide a soil sampling system for reducing the amount of friction between the barrel sampler and the ground. It is another object of the invention to accomplish these goals by providing a soil sampling system wherein the vibratory drill only drives the barrel sampler in the downward direction during the drilling process.